Seeking advice prior to purchasing a camper conversion

[travelling]

I have been looking around for a camper van. It appears that many of the vans are conversions of Transits.
I know this is a pretty broad question. Are there any particular models, years to avoid or other rules of thumb that may help?

[tbird]

We've been really pleased with our Autosleeper Flair. Not had a van before so can't comment on any others. The thing I like about our van is that with it being older it's easy to work, parts are relatively cheap and parts are readily available.